Conventionally, in a general camera with interchangeable lenses, it is necessary to connect a lens unit and a camera body not only optically but also electrically in order to perform communication and electric supply between them. For this reason, mount portions of the lens unit and the camera body are provided with terminals. The mount portion is restricted regarding its size to some extent. Thus, various problems are caused in disposing the terminal on the mount portion. For the purpose of solving these problems, many inventions concerning the disposition of the terminal have been made.
For example, there is a technique (see Japanese Patent Laid-Open Publication No. 02-163728) in that terminals of a camera-body side are disposed around an optical axis and at least two electric-supply terminals having different height are provided in a contact direction so as to form a step in this direction. At a position perpendicular to the contact direction of the camera-body-side terminal, a protrusion projecting from the connect terminal in the contact direction is formed. Moreover, a cutout is formed at a position which opposes to the protrusion at a time when both mounts are joined and separated.
In this technique, the mount portion of the camera-body side is provided with the electric-supply terminals disposed at the stepwise positions. Thus, at a time of detaching the lens unit, the electric-supply terminal is prevented from coming into contact with the other terminal and electrically shorting therewith. Since this technique concerns the terminals having different height, it is impossible to adopt this technique to an uneven shape.
Meanwhile, there is an interchangeable lens in which an interval of the electric-supply terminals is set so as to be different from that of the other terminal (see Japanese Patent Laid-Open Publication No. 58-83824, for instance). The respective terminals of the mount portion of the lens-unit side are biased by a biasing member so as to be connected to the respective terminals of the camera-body side. At the same time, the terminals of the lens-unit side are disposed on an identical circle located in a plane perpendicular to an optical axis of a lens, and the terminals are adapted to slide at a time of a rotational operation.
In this technique, the disposition distances of the terminals are different from each other so as not to contact a power source and the ground with a signal line at a detaching time of a lens unit for the purpose of preventing electrical short circuit.
In the meantime, a camera comprising a lens unit and a camera body is known (see Japanese Patent Laid-Open Publication No. 2000-175089, for instance). The lens unit includes a shooting optical system and an image sensor. The camera body to which the lens unit is detachably attached receives an image signal from the lens unit and performs signal processing.
Regarding the camera such as described in the above-noted Publication No. 2000-175089, the lens unit is likely to be detached from the camera body while a taken image is recorded. If the lens unit is detached from the camera body, a protective function does not work and not only the currently recorded image information but also all image information stored in a recording medium are likely to be destroyed. If the lens unit is accidentally or purposely detached from the camera body during the recording, the terminals disposed on both of the lens unit and the camera body are suddenly disconnected. Due to this, a surge voltage having a large momentary peak value is applied to both internal circuits from the terminal side. This is the reason why the image information is destroyed. However, there is no description concerning this problem in all of the above-noted Publications.